Forest Grazing and Natural Regeneration in a Late Successional Broadleaved Community Forest in Bhutan
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Mountain Research and Development (MRD) MountainResearch An international, peer-reviewed open access journal Systems knowledge published by the International Mountain Society (IMS) View metadata, citation andwww.mrd-journal.org similar papers at core.ac.uk brought to you by CORE provided by Mountain Forum Forest Grazing and Natural Regeneration in a Late Successional Broadleaved Community Forest in Bhutan Bill Buffum1*, Georg Gratzer1, and Yeshi Tenzin2 * Corresponding author: [email protected] 1 Institute of Forest Ecology, University of Natural Resources and Applied Life Sciences, Peter Jordan-Straße 82, A-1190 Wien, Austria 2 Mongar Range Office, Department of Forests, Mongar District, Bhutan This study investigated decreased and the number of naturally regenerated tree the sustainability of seedlings and saplings significantly increased. There were no combining forest grazing other changes in forest management practices during the and timber harvesting period that would affect natural regeneration, and there were with selection felling in no significant changes in the volume of wood harvested or a cool broadleaved the volume/number of standing trees (with a diameter at community forest (CF) in breast height $10 cm). We concluded that moderate Bhutan. Forest grazing intensities of forest grazing (0.4 cattle*ha21) and timber and timber production harvesting (4.64 m3*ha21*y21) can be combined in this are critical livelihood type of forest without negative impacts on forest activities for many farmers throughout the world, so it is regeneration. Our findings support Bhutan’s policy of important to understand under what conditions the 2 allowing forest grazing in CFs. activities can be combined. The study was based on a household survey to quantify livestock holdings and grazing Keywords: Community forestry; forest regeneration; patterns, a comparison of 2 forest inventories to assess selection felling; forest policy; cattle grazing; Bhutan. forest structure and regeneration, and a study of stumps to quantify harvesting intensities. During a 5-year period the Peer-reviewed: November 2008 Accepted: December number of cattle grazing inside the CF significantly 2008 Introduction In Bhutan cattle are owned by 90% of households (Norbu 2000). Forest grazing contributes 22% of the Forest grazing is practiced in many parts of the world. In national fodder requirement (Roder et al 2002) and is a the European Alps, 15% of mountain forests are grazed vital component of Bhutanese agriculture, providing a during summer (Mayer et al 2006), whereas in the United critical source of phosphorous via manure (Roder et al States more than 75% of forests in some states have 2003). However, forest grazing is widely considered to grazed for 2centuries (Wray 1998). Forest grazing negatively affect the natural regeneration of broadleaved reportedly has negative impacts on forest ecosystems, tree species in Bhutan (Van Ijssel 1990; Norbu 2000). such as soil erosion, depletion of nutrients, soil Forest grazing after logging operations led to the compaction, and soil acidification (Belsky and Blumenthal replacement of valuable timber species with unpalatable 1997; Barnes et al 1998). Forest grazing has been reported nontimber species (Chamling and Pushparajah 1993; to cause tree damage through trampling and browsing Davidson 2000; Seydack 2000). Positive effects of forest (Palmer et al 2004; Mayer et al 2006; Vandenberghe et al grazing have also been documented: forest grazing 2007) and loss of species richness and diversity (Fleischner promoted regeneration of tree seedlings in conifer forests 1994). In Switzerland, several cantons have enacted forest when grazing intensity was not too high (Gratzer et al laws to discourage the practice of forest grazing (Mayer et 1999; Darabant et al 2007). al 2006). This study attempted to assess whether forest grazing However, many authors argue that forest grazing can and timber harvesting with selection felling can be be sustainable if grazing intensity is controlled (Krzic et al combined sustainably in a cool broadleaved forest in 2001; Pollock et al 2005; Mayer and Huovinen 2007). Bhutan. Even though forest grazing is widespread in Forest grazing can enhance tree growth by reducing the Bhutan, the intensity and impact of grazing has not yet been biomass of grasses and sedges that otherwise outcompete adequately quantified (Norbu 2000). This research was part tree seedlings (Belsky and Blumenthal 1997; Gratzer et al of a larger study that also investigated the impact of 1999; Darabant et al 2007). Grazing has also been reported traditional harvesting practices on the diameter to promote biodiversity (Mitchell and Kirby 1990; distribution of the forest, diversity of tree species, and bole Mountford and Peterken 2003). shape and form of remaining trees (Buffum et al 2008). Mountain Research and Development Vol 29 No 1 Feb 2009: 30–3530 http://dx.doi.org/doi:10.1659/mrd.991 ß 2009 by the authors & IMS MountainResearch Description of research area legally established (2000). Although Bhutanese farmers can be reluctant to provide cattle numbers (Norbu 2000), Bhutan is a land-locked Himalayan country bordering we believe that the survey data are reliable because of the with China (Tibet) and India, with an area of 40,006 km2 participation of village leaders and the positive relations and an estimated population of 672,425 (RGOB 2005). with the community of one of the authors who served as Yakpugang community forest (CF) is located in the the local forestry extension agent. Mongar District of eastern Bhutan (27u159N; 91u169E) and ranges in elevation from 1800–3200 m. Rainfall data are 2005 Forest inventory not available for the Yakpugang area, but the annual We conducted a forest inventory in 3 blocks of the CF that rainfall is estimated to be up to 3000 mm (Mongar had similar site conditions and harvesting intensities. Dzongkhag 2001). The forest is classified as a cool Each block had a rectangular shape with a narrow base broadleaved forest (Grierson and Long 1983). It is (150 m) and longer sides (700 m) running up the slope, dominated by Quercus and Castanopsis and includes at least which included a greater harvesting intensity in the lower 32genera of tree species. The 260-haCF was originally portion of the block (closer to the village). In each block, part of the adjacent 13,840-ha Korilla Forest Management we established a systematic sample of 12temporary Unit (FMU), which is commercially managed with cable inventory plots (total of 36 plots) in a regular grid ranging crane logging operations. The CF was legally handed over in elevation from 1920–2430 m. to 113 households in 2001 through the new national Each inventory plot included a 25 m 3 10 m subplot in community forestry program, which receives support which all stems with height $1.3 m were measured. The from the Swiss Agency for Development and Cooperation plot layout followed the 1995 Department of Forests through the Participatory Forestry Management Project. (DOF) guidelines for CF inventories (Demanski 1995), It was the second CF approved in Bhutan and the first to which were also used in a 2000 forestry inventory of the start timber harvesting operations. The CF is managed for CF. The plots were laid out with the long sides timber, firewood, nonwood forest products, and forest perpendicular to the slope and with a 5 m 3 5m grazing. Cattle are the major source of grazing pressure in regeneration subplot in the center for seedlings with the forest. The local residents do not graze yaks, sheep, height ,1.3 m. We established 2additional subplots (25m goats, or horses in the forest. During the fieldwork we 3 7.5 m) plots above and below each plot for additional observed signs of wild boar (Sus scrofa) near the village, data on timber-size trees (30 cm diameter at breast height heard 1 barking deer (Muntiacus muntjak), and were [dbh] or greater). We recorded the species, diameter, and informed that sambar (Cervus unicolor) is occasionally seen, estimated age of all stumps in the entire 25 m 3 25m but we did not observe signs of these animals in any of the plots. inventory plots. Tree volume was calculated using volume tables prepared for the adjacent Korilla FMU (FAO 1993). The Methodology annual allowable cut (AAC) for the current study was calculated using the approach of the management plan Research approach for Korilla FMU: AAC 5 (net operable area/rotation The study was based on a comparison of 2forest period) 3 (average standing volume/ha) (DOF 2005) and inventories during a 5-year period and a household survey the same rotation period of 100 years. This method to assess changes in livestock holdings and grazing assumes that all trees are removed, and our study of patterns. Yakpugang CF was an ideal location for the stumps verified that the villagers harvest a range of size study because the grazing intensity was quantifiable due classes, with the largest number of stumps in the 10–14 cm to a fixed number of households that utilize the forest and dbh class, as can be seen in Figure 1. geographic features that delineate its borders. The age of the stumps was estimated with the Furthermore, a forest inventory had been conducted in assistance of 2local residents who were very familiar with the same forest 5 years earlier. Replication of the study in logging operations in the forest and had worked as additional forests would have strengthened the study, but professional loggers in the adjacent commercially we could not identify another broadleaved forest with managed FMU. For each stump, a team of 3–4 persons baseline forest inventory data and a quantifiable forest estimated the year of harvesting by cutting into the stump grazing intensity. with a machete and assessing the level of deterioration. We compared the AAC to the volume harvested during 5- Household survey year periods, but only included stumps harvested during The household survey was administered to a random the past 20 years as we were less confident about the ages sample of households stratified by hamlet and of the older stumps.